Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee

Kawahito, Yousuke; Mizutani, Masami; Katayama, Seiji

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タイトル	Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee
著者	Kawahito, Yousuke Kawahito, Yousuke
	Mizutani, Masami Mizutani, Masami
	Katayama, Seiji Katayama, Seiji
キーワード等	High-power fiber laser
	Laser-induced plume
	Stainless steel
	high-speed observation
	Spectroscopic analysis
	Laser probe measurements
抄録	The objective of this research is to obtain a fundamental knowledge of the optical interactions in a 10-kW fiber laser beam of 0.9-MW/㎟ power density and the plume or plasma induced during bead-on-plate welding of 20-mm-thick Type 304 stainless steel plate, on the basis of high-speed video observations, spectroscopic analysis and laser probe measurements. According to the high-speed observation results, the laser-induced plume was repeatedly generated from a keyhole at intervals of about 0.5-ms. The spectroscopy indicated that a bright plume emitted the line spectra of neutral atoms of alloying elements in Type 304 such as iron (Fe), chromium (Cr) and manganese (Mn). The temperature and the ionization degree of the laser-induced plume were calculated to be approximately 6,000 K and 0.02, respectively, by the Bolzman plots and via Saha’s equation. Furthermore, the probe laser passed horizontally through the plume was refracted at 0.6-mrad angle on average, which was much lower than the 90-mrad divergence of the focused fiber laser beam. The attenuation of the probe laser was measured to be about 4%, which was not mainly caused by Inverse Bremsstrahlung but by Rayleigh scattering. Subsequently, a stable laser welding process could be established at such an ultra-high power density that 11.5-mm-deep penetration was obtained even if the laser peak power was modulated 1-ms-periodically from 10 kW to 8.5 kW. It was consequently considered that the optical interaction between the 10-kW fiber laser beam and the weakly-ionized plume was too small to exert a reduction in weld penetration.
公開者	大阪大学接合科学研究所
公開者の別表記	Joining and Welding Research Institute, Osaka University
公開者 (ヨミ)	オオサカダイガクセツゴウカガクケンキュウジョ
掲載誌名	Transactions of JWRI
巻	37
号	2
開始ページ	19
終了ページ	25
刊行年月	2008-12
ISSN	03874508
NCID	AA00867058
URL	http://hdl.handle.net/11094/5073
言語	英語
カテゴリ	紀要論文 Departmental Bulletin Paper
カテゴリ	Transactions of JWRI / Vol.37 No.2 (2008-12)

著者版フラグ	publisher
NII資源タイプ	紀要論文
ローカル資源タイプ	紀要論文
dcmi資源タイプ	text
DCTERMS.bibliographicCitation	Transactions of JWRI.37(2) P.19-P.25
DC.title	Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee
DC.creator	Kawahito, Yousuke
	Mizutani, Masami
	Katayama, Seiji
DC.publisher	大阪大学接合科学研究所
DC.language" scheme="DCTERMS.RFC1766	英語
DCTERMS.issued" scheme="DCTERMS.W3CDTF	2008-12
DC.identifier" scheme="DCTERMS.URI	http://hdl.handle.net/11094/5073
DC.subject	High-power fiber laser
	Laser-induced plume
	Stainless steel
	high-speed observation
	Spectroscopic analysis
	Laser probe measurements
DCTERMS.abstract	The objective of this research is to obtain a fundamental knowledge of the optical interactions in a 10-kW fiber laser beam of 0.9-MW/㎟ power density and the plume or plasma induced during bead-on-plate welding of 20-mm-thick Type 304 stainless steel plate, on the basis of high-speed video observations, spectroscopic analysis and laser probe measurements. According to the high-speed observation results, the laser-induced plume was repeatedly generated from a keyhole at intervals of about 0.5-ms. The spectroscopy indicated that a bright plume emitted the line spectra of neutral atoms of alloying elements in Type 304 such as iron (Fe), chromium (Cr) and manganese (Mn). The temperature and the ionization degree of the laser-induced plume were calculated to be approximately 6,000 K and 0.02, respectively, by the Bolzman plots and via Saha’s equation. Furthermore, the probe laser passed horizontally through the plume was refracted at 0.6-mrad angle on average, which was much lower than the 90-mrad divergence of the focused fiber laser beam. The attenuation of the probe laser was measured to be about 4%, which was not mainly caused by Inverse Bremsstrahlung but by Rayleigh scattering. Subsequently, a stable laser welding process could be established at such an ultra-high power density that 11.5-mm-deep penetration was obtained even if the laser peak power was modulated 1-ms-periodically from 10 kW to 8.5 kW. It was consequently considered that the optical interaction between the 10-kW fiber laser beam and the weakly-ionized plume was too small to exert a reduction in weld penetration.
citation_title	Optical Interaction between Laser Beam and Induced Plume in the Ultra-High Power Density Fiber Laser Welding of Stainless Stee
citation_author	Kawahito, Yousuke
	Mizutani, Masami
	Katayama, Seiji
citation_publisher	大阪大学接合科学研究所
citation_language	英語
citation_date	2008-12
citation_journal_title	Transactions of JWRI
citation_volume	37
citation_issue	2
citation_firstpage	19
citation_lastpage	25
citation_issn	03874508
citation_public_url	http://hdl.handle.net/11094/5073
citation_keywords	High-power fiber laser
	Laser-induced plume
	Stainless steel
	high-speed observation
	Spectroscopic analysis
	Laser probe measurements

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